There are great savings to using an aftermarket rotor. They can probably be bought for half MB list.
The pads are another story. The pads can probably be bought for a quarter of MB list but they are not expensive compared to other cars and the composition of the material (among other things) makes the final job. We use only MB pads on late model cars and they are cheaper than the Honda pads we stock from the Honda dealer.
There are a number of good manufacturers for brake pads and if you know which to buy you can save money and get good results. If not, buying from MB assures you of the right composition pad.
We did some brakes on a friend's late model Ford truck recently. Not knowing which parts to use, I called a friend that does that kind of work regularly. I find out that these brakes are underdesigned and are notorious for front brake problems due to overheating. My friend offered to call our common local source and order the pads for me.
They were Raybestos "Extreme Duty" pads and had to be ordered as they only stocked two grades of Raybestos pads for this most common 3/4 ton pick-up. Neither grade they stocked met the standard found to be successful by my friend who has the type of experience that I might have with German cars.
There is more to fixin cars than just turnin the wrenches!
Bosch Master, ASE Master, L1
33 years MB technician